This invention relates to a high-voltage electric circuit breaker that comprises a plurality of circuit interrupters that are electrically connected in series and are opened substantially simultaneously during a circuit-interrupting operation. More particularly, this invention relates to a circuit breaker of this type in which at least one of the interrupters is a vacuum-type circuit interrupter and the remaining interrupter or interrupters are of the fluid blast type. A circuit breaker of this general type is disclosed in U.S. Pat. No. 3,244,842-Kameyama et al.
In a high-voltage circuit breaker that utilizes series-connected interrupters, it is customary to provide voltage-grading means for distributing the circuit-breaker voltage in the desired manner between the interrupters. Such voltage-grading means typically comprises capacitors of appropriate size connected across the individual interrupters. Such voltage-distributing capacitors are relatively expensive, and it would be highly advantageous if they could be eliminated or at least reduced in number.
Accordingly, an object of my invention is to eliminate the need for at least some of the voltage-distributing capacitors that are typically connected across the individual interrupters of a circuit breaker comprising series-connected interrupters.
For improving the ability of a high-voltage circuit breaker to withstand the recovery voltage transient that is developed thereacross when the circuit breaker attempts to interrupt at a current zero, it is conventional to connect across the interrupters of certain high-voltage circuit breakers a relatively low-impedance capacitor or resistor that is effective to lower the rate of rise of the recovery voltage transient. This low-impedance capacitor or resistor is in addition to the above-described voltage-distributing capacitors.
Another object of my invention is to eliminate the need for such a low-impedance capacitor or resistor for reducing the rate of rise of the recovery voltage across the circuit breaker, as well as eliminating the need for at least some of the voltage-distributing capacitors across the individual interrupters.